It’s almost like “Another month, another Viltrox lens”. Viltrox is releasing new lenses almost at breakneck speed. This time, we’ll discuss the Viltrox AF 25mm f/1.7 XF Air. It’s an APS-C format lens available for Sony E-, Fujifilm X- and Nikon Z-mount. This moderate wide-angle lens is available for an MSRP of $176 / €189 / £165. Let’s see whether they can maintain their impressive track record of late with this lens as well.
Build-quality-wise, it’s a typical “Air” lens. Viltrox has 3 different line-ups – “LAB”, “PRO” and “Air” – with the latter focusing on affordable products. However, affordable doesn’t mean cheap here. It’s not comparable to their Pro lenses, of course, but while very lightweight (thus the “Air”), the plastic quality of the lens body feels decent for its class. It has a metal mount, and it uses internal focusing, so there’s at least a limited protection against the elements. Formal weather-sealing is not provided, though. The focus ring turns smoothly. There are no further buttons or switches found on the lens, so if you want to disable the AF, you’ll have to do it via the camera. A petal-shaped lens hood is provided.
The Viltrox AF 25mm f/1.7 XF uses a stepping motor for autofocusing. It’s very fast (on an X-H2) and silent. As usual, manual focusing works “by-wire”. Firmware updates are possible via a USB-C port on the mount.
| Specifications | |
|---|---|
| Optical construction | 12 elements in 10 groups (1x ED, 2x HR, 2x, aspherical) |
| Number of aperture blades | 9 |
| min. focus distance | 0.3 (max magnification 0.11x) |
| Dimensions | φ64×54.7mm |
| Weight | 170g |
| Filter size | φ52mm |
| Hood | petal-shaped (bayonet mount, supplied) |
| Other features | USB-C port for firmware updates |
Distortions
As with most Viltrox lenses, the AF 25mm f/1.7 XF is mostly optically corrected with respect to image distortions. In RAW images, you may spot a minor barrel distortion of just under 1%. Autocorrection was not provided in our sample, but may be added via firmware updates.
Vignetting
The vignetting is relatively high (for an APS-C lens) – and there’s no correction profile for this. At f/1.7 the light falloff exceeds 1.1 EV (f-stop). As usual, stopping down helps, and the issue is mostly resolved from f/28 onward.
MTF (resolution) at 26 megapixels
The resolution characteristic of the Viltrox AF 25mm f/1.7 XF is pretty good. At f/1.7 the center performance is already excellent. There is a drop outside the dead center. However, even the outer image field is Beyond the still good to very good, though. Stopping down lifts the overall quality slightly until reaching its peak around the f/2.8 mark. Diffraction has a higher impact beyond f/8.
The centering quality of the tested sample was Okay. The field curvature is a bit “wobbly” midfield.
Please note that the MTF results are not directly comparable across the different systems!
Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure of sharpness. If you want to know more about the MTF50 figures, you may check out the corresponding Imatest Explanations.
Chromatic Aberrations (CAs)
Lateral CAs are elevated without being extreme. They reach an average pixel width of 1.5px at the image borders. Without autocorrection, this may be noticeable at times.
Bokeh
A 25mm f/1.7 APS-C lens may appear fast on paper, but in full format terms, it’s comparable to a 38mm f/2.5. As such, its bokeh capabilities are a bit limited, and you’ll need fairly close focus distance to achieve a shallow depth-of-field. Regardlessly, let’s take a look at out-of-focus highlights, at least.
The inner zone of the highlight discs is fairly clean, with only slight hints of nervousness injected by the 2x aspherical elements. The disc edges are quite smooth, and there’s no outlining when stopping down. The discs remain circular at f/2.8.
When looking at the highlight rendering across the whole image field, there are some obvious “cat eyes” from the midfield at f/1.7. The highlights in the outer image field do shows some disc outlining here. The outlining is reduced at f/2.2 and gone by f/2.8. The corner discs are also mostly restored to their circular shape at this setting.
Note: Usually we really show the whole image field, but the lens can’t focus close enough for producing decent background bubbles – so the images below show a sample crop of the upper left quadrant.
Bokeh Fringing / LoCA
LoCAs, or bokeh fringing, is a color fringing effect on the Z-axis. It shows up with a purplish tint in front of the focus point and a greenish tint behind – and it’s nearly impossible to fully correct in post.
As you can see below, the Viltrox lens does show some color fringing at f/1.7. Traces remain at f/2.8, and the issue is basically gone from f/4.
If you look closely, you may spot a marginal focus shift towards the rear when shopping down.
Sun Stars
Sun stars/rays are an aperture effect when stopping down – introduced by an increasingly edgy aperture shape. They occur when shooting images with very bright light sources such as the sun or streetlights at night.
As you can see below, there are relevant rays visible from f/1.7 up to f/5.6 because the aperture is still (near-) circular at these settings. Traces of rays are more obvious from f/8 with the best results at f/16. The rays are somewhat “fan-like” which is less ideal than pointy rays. However, the manufacture has to set priorities – you can either have circular bokeh highlights or nice sun stars – but rarely both.
Competition
There are a number of moderate wide-angle lenses available in Fujifilm X-mount. The most obvious competitor to the Viltrox AF 25mm f/1.7 XF is the Fujinon XF 23mm f/2 WR. It’s marginally wider, but also a bit slower. It feels more “substantial” in comparison, and it does have weather sealing plus a dedicated aperture ring. Optically, it isn’t any better, though. The Sigma 23mm f/1.4 DC DN also comes into mind. Conceptually, it is similar but much faster and as such bigger – and much more expensive. On the more exotic side, there’s the Sirui 23mm f/1.2 and the TTArtisan AF 23mm f/1.8. These are interesting in terms of costs, but without having tested them, they are difficult to judge from our side.
Sample Images
The Viltrox AF 25mm f/1.7 XF Air produced very decent results during our testing. In terms of lab performance, the achieved center resolution is excellent straight from f/1.7, and outer image field still on a good to very good level. Stopping down broadens the quality near the center, and the results are very good overall around the f/2.8 mark already. The focus field is a bit wavy, though, so stopping down a bit further is advisable for "infinity" scenes. Lateral CAs are somewhat elevated, although you should be able to handle this during post-processing if needed. The vignetting is high at f/1.7 - albeit rather normal for a fast prime lens - but mostly negligible from f/2.8. Unfortunately, there's no built-in correction profile at the time of this review, at least. Hopefully, Viltrox will provide a firmware update for this at some point. You shouldn't expect wonders in terms of bokeh from an APS-C wide-angle lens. However, in close focus scenarios, it can deliver a quite smooth out-of-focus blur. Keep in mind that the maximum magnification is a bit limited at 1:9, so the close focus capabilities are a bit limited.
Viltrox Air lenses are targeting the consumer segment. For a lens in this class, the build quality may be simple, but it's also pretty good. The body is based on decent quality engineered plastics based on a metal mount. The (plastic) focus ring turns smoothly and there's no wobbling whatsoever. Weather sealing is not provided here, but the internal focusing should help a bit in terms of protection. The AF is surprisingly fast and quiet.
Viltrox AF 25mm f/1.7 XF Air follows the tradition of its in-house "Air" cousins - it provides good optical and mechanical qualities at an attractive price point.
The Good
- Pretty sharp
- Very affordable
- Decent build quality for its price class
- Snappy AF
The Bad
- No autocorrection profile
- Max magnification (close focus) could be better
-
Optical Quality
-
Build Quality
-
Price / Performance